The Digestive System: Biological Functions

The digestive system serves important biological functions within the body. Food must be processed in three ways: digestion, absorption, and elimination. The digestive system is responsible for the accomplishment of all three of these biological functions. All food ingested must be digested, nutrients absorbed, and unnecessary or harmful agents eliminated from the body.

Digestive System: The Food Journey

The journey of the food we eat through the digestive system is more complicated than one might credit. The journey begins with ingestion into the mouth, where mechanical digestion occurs, and food passes through the pharynx into the esophagus. From the esophagus, food travels into the stomach, where the majority of chemical digestion takes place. From the stomach, food travels to the small intestine, where the majority of nutrient absorption occurs.

After the small intestine, the large intestine prepares unused food for excretion through the rectum and anus. The digestive system is also associated with many accessory organs, responsible for producing an array of chemical enzymes; salivary glands, pancreas, liver, gallbladder.

Mechanical Digestion

Mechanical digestion is the first step of the digestion process and begins immediately after ingestion. Mechanical digestion is the actual process of mastication (chewing) of food by teeth, to break the ingested food into smaller pieces that are more readily digested through chemical digestion.

This mastication is mixed with saliva, which contains some enzymes to begin the chemical digestion process. Mechanical digestion also involves the process known as peristalsis. Peristalsis is accomplished by smooth muscle within the body and is responsible for the movement of food through the intestinal tracts.

Chemical Digestion

Chemical digestion is accomplished through the use of chemicals known as digestive enzymes. These enzymes and water are responsible for the breakdown of complex molecules. These complex molecules, such as fats, proteins, and carbohydrates, are digested (broken down) into smaller molecules. These smaller molecules can then be absorbed for use by cells.

Digestive enzymes control reaction speed. The presence of these digestive enzymes accelerates the digestion process, where absence of these enzymes slows overall reaction speed. Currently, there exist eight digestive enzymes mainly responsible for chemical digestion.

• Nuclease
• Protease
• Collagenase
• Lipase
• Amylase
• Elastase
• Trypsin
• Chymotrypsin

Digestion: How Long Does it Take?

The amount of time necessary to process food through mechanical and chemical digestion varies by individual circumstances. In healthy adults, this process can range from 24-72 hours. Typically, after ingestion, food remains in the stomach and small intestine from 6-8 hours. The large intestine is capable of holding undigested food waste for days.

A Necessary Equilibrium: Mechanical and Chemical Digestion

There exists a natural equilibrium in your body for mechanical and chemical digestion. Mechanical digestion preps food for chemical digestion, as smaller pieces are more readily broken down and absorbed. The enzymes necessary for proper chemical digestion are also in an equilibrium. The accessory organs of the digestive system necessary for the production of these enzymes must all work in a harmonious fashion to accomplish proper digestion.

Prolipamy digestive enzyme complex for maximum health.

Sources:
http://www.mayoclinic.com/health/digestive-system/AN00896
http://www.webmd.com/digestive-disorders/digestive-system